1. Field of the Invention
The present invention relates to a laser therapeutic apparatus for use in the field of laser therapies such as photodynamic therapy (PDT).
2. Related Background Art
With the recent progress of optical technologies, photodynamic therapy (PDT) has attracted attention. PDT is a therapeutic method which combines a laser and a photosensitive drug which specifically builds up in a proliferative tissue. By irradiating a lesion with a laser beam, a tumor tissue or neovascularization can be selectively destroyed or occluded without any thermal effect. For example, when a certain kind of photosensitive drug is administered to a patient beforehand and the lesion is irradiated with a laser beam, only tumor cells die with no influence on healthy cells. Also, it is being attempted to limit an irradiation region to a lesion by controlling the shape of a laser beam.
A laser therapeutic apparatus described in Japanese Patent Laid-Open No. 6-63164 is capable of controlling the shape of a laser beam and used in PDT. In this apparatus described in Japanese Patent Application Laid-Open No. 6-63164, a fluorescent image generated in a living body when the body is irradiated with a laser beam is sensed, the shape of a lesion is specified from the obtained fluorescent image, and a light transmitting region of a liquid crystal shutter is set in accordance with the specified shape. After that, the lesion is irradiated with a laser beam for treatment through the liquid crystal shutter. The liquid crystal shutter has a nematic liquid crystal or the like whose alignment direction changes depending on the applied voltage. By adjusting the applied voltage, therefore, the transmittance of a linearly polarized laser beam entering the liquid crystal can be controlled.
In the apparatus described in Japanese Patent Application Laid-Open No. 6-63164, however, the shape of a laser beam is controlled by passing the laser beam through the liquid crystal shutter. Accordingly, the transmittance is about 50% for a linearly polarized laser beam and about 25% for an unpolarized laser beam. The present invention has been made to solve the above problem, and has as its object to provide a laser therapeutic apparatus capable of emitting a laser beam at high efficiency.
To achieve the above object, a laser therapeutic apparatus of the present invention is a laser therapeutic apparatus for irradiating a region to be treated with a laser beam, comprising a reflecting spatial light modulator which displays a predetermined pattern, a laser light source which irradiates the spatial light modulator with a laser beam, and an optical system so positioned that the laser beam reflected by the spatial light modulator irradiates the region to be treated.
When the above configuration is used, the reflectivity of the laser beam can be well raised compared to an apparatus which uses a transmitting device, so laser beam irradiation can be performed at high efficiency.
The predetermined pattern is preferably a hologram pattern so set that in a region to be treated, the laser beam reflected by the spatial light modulator has the same shape as an image of this region to be treated. In this case, a totally reflected laser beam can be effectively used.